There is a conventional device in which a combustible gas is generated by a combustible gas generator, the combustible gas is discharged from a combustible gas discharge port to an exhaust passage in the upper stream of a DPF, a temperature of an exhaust gas is raised by combustion heat generated by burning the combustible gas using oxygen in the exhaust gas, and a PM accumulated in the DPF is burnt and removed by the heat of the exhaust gas (refer to Patent Document 1).
This type of a device is advantageous in that the PM accumulated in the DPF can be burnt and removed by raising the temperature of the exhaust gas by using the combustible gas even when the temperature of the exhaust gas is low.
The conventional technology, however, is problematic in that a thermal conduction plate and the central wall of an air-fuel mixing chamber are interposed between the heat-dissipating outer peripheral surface of a heater and the air-fuel mixing chamber and thus heat is indirectly radiated from the heat-dissipating outer peripheral surface of the heater to the air-fuel mixing chamber sequentially through the thermal conduction plate and the central wall of the air-fuel mixing chamber when the generation of the combustible gas is started.